Do you get some type of Windows Error message or something when attempting to use the Apploader.exe?

I would suggest uninstalling DM as well as all Blackberry related software from your computer (minus the back-up save files) and then attempt a re-install. I have herd of this issue happening to others, and this was the method used to resolve the issue. They also used a Registry Edit program to sift there registry for bad links to the original installation so that it was "truly wiped" from there PC.